MilkDrop is a music visualizer - originally a "plug-in" to the Winamp music player, and now available as OSS.
As you listen your music in Winamp, MilkDrop 2 takes you flying through visualizations of the soundwaves you're hearing, and uses beat detection to trigger myriad psychedelic effects, creating a rich visual journey through sound. MilkDrop 2 can also be driven by a live audio feed (microphone or line-in) - see the documentation for details.
Amazing visualizer. Hands down the best one I've ever seen. It truly is out of this world even though some times it can be a bit "off" PS: For the "Support" I'm not giving a rating as I have not requested or searched for any support